In our laboratory a reliable animal model of disciform keratitis, presenting a clinical syndrome very similar to the human disease, has recently been described. Ultrastructural and immunohistochemical studies of disciform keratitis in the animal model, and in human corneas obtained from patients who have received corneal transplants for chronic herpetic keratitis are presently in progress. We have shown that viral antigens are present in the diseased corneas although viral proliferation is not occurring. A major corneas is the lymphocyte, and many of these cells are found in close contact with degenerating keratocytes. These observations represent the first direct evidence that disciform keratitis results from a cell-mediated immune reaction. During the coming year, we plan to continue histological, ultrastructural and immune cytochemical studies to describe the development of disciform keratitis in experimental animals, and to correlate the observed pathological features with those found in human corneas obtained from patients with recurrent herpetic stromal keratitis. Further definition of histological and immunological events associated with the development and recurrence of herpetic stromal keratitis should lead to improved clinical management of this blinding disease.